The present invention relates to doors.
More particularly, the present invention is concerned with doors for vehicles.
It is known in the prior art to provide a vehicle with a door having at least one door section which is slidable along an outer side wall of the vehicle between a closed position and an open position. When the door section is in the closed position, it swings into the outer side wall. It is also known to provide a bearing rail which extends horizontally and parallel relative to the side wall. The door section slides along such a bearing rail between the open and closed positions. The door section is supported (i.e. suspended) on the bearing rail by means of an attachment plate which is provided with guide rollers which are positively locked (i.e. engaged) with the bearing rail. The door section is able to swing in a direction which is transverse to a direction of the sliding movement of the door section along the bearing rail.
In German Patent No. 1 081 324 it has been suggested, for example, to suspend a door section on an attachment plate which is provided with two double conical guiding roller units. The roller units are located on the attachment plate as to surround a tubular supporting rail at the opposite sides thereof. The supporting rail has a circular cross-section. The rail extends horizontally and parallel relative to and is fixedly connected to a side wall of a vehicle. Thus, the rail functions as a guide element for the door section to be kept in parallel to itself, and such a suspension arrangement of the door section takes up all possible vertical stresses (i.e. loads) stipulated by the weight of the door section itself in particular and all the supporting elements in general.
The drawback of such a door becomes especially apparent when it is necessary to displace the latter in the open position by way of transversally moving the door section outward. During such a movement of the door section, the double conical rollers frictionally rotate about the rigid stationary supporting rail. Obviously, it is necessary to increase the pulling force correspondingly so as to overcome a counterforce in the frictional engagement between the rollers and the supporting rail. Moreover, the friction between the rollers and the rail during the movement of the door section absolutely improductively leads to an additional wear (i.e. abrasion) of the rollers and the rail. This fact is most likely to result in reducing the service life of the rollers and the rail in particular and the door in general. It goes without saying that the same negative results occur during the movement of the door section from the open into the closed position.
In Austrian Patent No. 242 738 it has been suggested to provide a door having an outward movable door wing which is operatively connected to a supporting rail so that the latter may displace together with the door wing and relative to a side wall of a vehicle. The supporting rail is provided at the respective ends thereof with supports for pivoting relative thereto. During pivoting movement of the rail between the open and closed positions of the door, the rollers disadvantageously frictionally rotate along the outer surface of the supporting rail.